The present invention relates to a method for making an electrical circuit board and more particularly, to a method for making a multi-layer electrical circuit board having multiple circuit interconnections and having apertures and/or cavities which are formed within the circuit board and/or through various portions of the circuit board.
Multi-layer circuit boards contain and/or include electrical components which selectively and operatively populate opposed first and second surfaces (i.e., top and bottom surfaces) of each board (or other respective interior portions of each of the boards), thereby desirably allowing each of the electrical circuit boards to contain and/or include a relatively large amount of electrical components which efficiently and densely populate the respective boards.
It is desirable to allow for communication by and between and/or interconnection of the component containing surfaces and/or portions of an electrical circuit board, thereby allowing the contained electrical components on each side of the board (or within certain interior portions of the board) to cooperatively and selectively interconnect to form one or more desired electrical circuits. This communication and interconnection may require the use of shared electrical ground planes, the transmittal of electrical power and/or control type signals between each of the component containing surfaces and/or the component containing board portions, and/or the selective and physical connection of various contained components.
This desired interconnection typically requires one or more holes or cavities to be drilled and/or formed through the core of the circuit board substrate, thereby selectively creating one or more xe2x80x9cthrough-holexe2x80x9d type vias (i.e., holes which pass and/or traverse the entire circuit board or all of the opposed component containing surfaces). The xe2x80x9cthrough-holexe2x80x9d type vias are then typically filled with solder (e.g., a pin or component connector is soldered into the hole). In this manner, electrical connections are made or formed which connect electrical components and/or circuitry to the core of the circuit board substrate, or to other components and/or circuitry located on the opposing side or surface of the board.
One drawback with these xe2x80x9cthrough-holexe2x80x9d type vias is that layers of relatively non-solderable material (i.e., material which does not substantially bind or metallurgically bond with solder) are typically present within these vias, and thus, the solder does not consistently and reliably electrically connect the desired layers of circuitry and/or components together. Additionally, the drilling required to form these xe2x80x9cthrough holexe2x80x9d type vias is undesirable since it is relatively time consuming, costly, potentially causes damage to significant numbers of the formed electrical circuit boards requiring these circuit boards to be destroyed, and requires costly and inefficient electroless and/or electrolytic plating of the formed holes or xe2x80x9cviasxe2x80x9d.
While some attempts have been made to obviate the need for such plating, these attempts have not produced reliable electrical interconnections and the produced interconnections are not typically adapted to allow for communication of electrical power signals by and between the board surfaces and/or the interior component containing portions.
For these reasons, xe2x80x9cblindxe2x80x9d type vias, apertures or cavities (i.e., holes which do not pass and/or traverse an entire circuit board or all of the opposed component containing surfaces) have been developed and utilized to make and/or form connections between portions and/or layers of a circuit board. The present application describes new and novel designs for such xe2x80x9cblindxe2x80x9d type vias or cavities, which selectively allow for the interconnection of one or more layers of electrical circuitry.
It is a first object of the present invention to provide a method for producing a multi-layer electrical circuit board, which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques.
It is a second object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques and which allows for the selective, efficient, and reliable formation of apertures which allow for communication by and between some or all of the various component containing surfaces and portions of the formed multi-layer electrical circuit board, which selectively allows components contained within and/or upon these portions and surfaces to be interconnected, and which is further adapted to selectively and communicatively receive an electrical component and/or an electrical component connector portion.
According to a first aspect of the present invention, a circuit board assembly is provided. The circuit board assembly includes an electrically conductive core member; first circuit portion connected to the core member; and an annular ring which is integrally formed within the first circuit portion and which forms a blind via within the circuit board assembly which extends to the core member.
According to a second aspect of the present invention, a second circuit board assembly is provided. The circuit board assembly includes a pre-circuit assembly having a core metal portion and a first and second electrically conductive member, a core electrically conductive member contained between a first layer of dielectric material and a second layer of dielectric material, the core member connected to the pre-circuit assembly by a first layer of adhesive and a third electrically conductive member connected to the core member by a second layer of adhesive, wherein certain portions of the core member, the third electrically conductive member, the adhesive layers and the dielectric material layers have been removed to form a blind via and an annular pad which surrounds the blind via.
According to a third aspect of the present invention, a method for making a circuit board is described. The method includes the steps of providing a core member having a first surface and a second surface; selectively applying a first certain dielectric material to the first surface of the core member; selectively applying a first adhesive material to certain selective portions of the first dielectric material; attaching a first electrically conductive member to the first surface of the core member using the adhesive material; and removing certain selective portions of the first electrically conductive member, the first dielectric material and the first adhesive material effective to cooperatively form a blind via.
These and other objects, aspects, and advantages of the present invention will become apparent upon reading the following detailed description in combination with the accompanying drawings.